An economizer is a common member in a large-scale refrigeration system and is used to enable throttling and evaporation of a part of a refrigerant to absorb heat, so as to enable another part of the refrigerant to achieve super-cooling. In many cases, the economizer may be used in a refrigeration system having a multi-stage compressor unit. In a working condition in which evaporation temperature is relatively low, a normal multi-stage compressor unit has various defects such as reduced efficiency, reduced refrigerating capacity, and relatively high exhaust temperature. If the economizer is used to perform air supplementation between compression stages of the multi-stage compressor unit, efficiency of refrigeration cycles can be improved, refrigerating capacity can be improved, and exhaust temperature of a compressor can be reduced.
An economizer is an essential member in a large-scale refrigeration system, and in the overall design of the refrigeration system, inevitably, an overall layout of the refrigeration system after the economizer is applied needs to be considered. The connecting pipe passages between the economizer and other members also need to be designed together. As a result, an overall layout of a large-scale refrigeration unit becomes troublesome and complex. In addition, complexity of disposing of pipe passages also indirectly affects running efficiency and reliability of the system.